Syringes used for delivery of medicaments are principally constructed of a barrel and a stopper. The stopper is slidably fitted within the syringe barrel and may have a stopper rod affixed to it for actuation of the syringe and delivery of medicament. The stopper is generally constructed of an elastomer, with silicone oil applied. The silicone oil is applied to the stopper or barrel to reduce sliding friction between the stopper and barrel and to improve the seal between them, which can be helpful in ensuring a full dose is administered. Ease of sliding can be important for proper operation of pens and so-called auto injecting syringes. The oil helps prevent jamming of such devices, which can otherwise lead to trauma at the site of injection. The improved sealing provided by silicone oil can also help ensure no foreign contaminants, such as bacteria, enter the syringe.
Recently there has developed a trend favoring pre-filled syringes which function to both store and deliver medicaments. Such pre-filled syringes may offer cost savings to the pharmaceutical industry and may improve safety, convenience and efficacy of medicament delivery. Biopharmaceuticals are an important class of pharmaceuticals that may increase the use of pre-filled syringes and related devices (pens, auto injectors and the like). Such biopharmaceuticals may include insulin, vaccines, antibodies, blood products, hormones, cytokines, and the like. As more pharmaceuticals and particularly biopharmaceuticals utilize delivery in pre-filled syringes and similar devices, the challenges of conventional syringe technology multiply.
Several aspects of traditional syringe construction present a challenge for their use as pre-filled syringes. The use of silicone oil is a concern, because the oil may degrade the medicament and because a small amount of silicone may be injected with it. The oil is of particular concern with regard to biopharmaceuticals because it may cause aggregation of certain proteins.
Another issue that arises in pre-filled syringes is that the elastomer of the stopper may contain leachable and extractable contaminants. These may also contaminate the medicament upon long term storage in syringes. Trace amounts of residual monomer or plasticizer or other impurities from the stopper can adversely affect the therapeutic function or can have an adverse impact on the patient once injected.
Among the many other considerations affecting pre-filled syringe devices and similar devices and their components are the need to be sterilized, stability with transport and storage for up to a few years, optical clarity, the need to integrate into existing filling equipment (including the durability requirements for stopper cleaning and insertion into the syringe barrel), leachables and extractables of all components of the syringe, and the need to maintain sterility from filling through administering of the contents, and finally user preferences and ergonomic considerations. For a variety of considerations the pre-filled syringe market uses both glass and plastic barrels.
Friction between stopper materials and syringe barrels can be significant. As described above, lubricants such as silicone oil are problematic. There is a need to reduce friction between stopper and barrel without the use of oils or other lubricants that have undesirable effects.